Common Water Heater Problems and What Causes Them
No hot water, a leak, a strange noise or a smell? Here’s what usually causes it and what to do next.
Most water heater trouble shows up in one of a few ways: no hot water, not enough, a leak, a noise or a smell. Find what you’re seeing below. Each problem lists the usual causes and what to do next. When in doubt, text us a photo of the label and tell us what’s happening.
No hot water
Gas water heater: pilot light out or won’t stay lit
What you notice: No hot water and no flame through the burner window.
Common causes: A worn thermocouple or thermopile, a dirty pilot, a failing gas control valve, or a tripped flammable vapor sensor on newer tanks.
What to do: If you’re comfortable, relight it by following the instructions on the tank’s label. If it goes out again, a part has failed. Text us the model number.
Gas water heater: burner won’t light
What you notice: You hear clicking, or the status light blinks a code, but no flame.
Common causes: A failed igniter or flame sensor, low gas supply, a bad control board, or a power-vent blower or pressure switch that stopped working.
What to do: Note the blink pattern or error code and text it to us with a photo of the label.
Electric water heater: no hot water at all
What you notice: Cold water from every hot tap.
Common causes: A tripped breaker, a tripped high-limit (reset) switch, burned-out heating elements or a failed thermostat.
What to do: Check the breaker once. If it trips again or the reset button keeps popping, stop and call us. Something is shorting.
Not enough hot water
Hot water runs out fast
What you notice: Showers go lukewarm sooner than they used to.
Common causes: Sediment filling the bottom of the tank, a broken dip tube mixing cold water into the hot, a failed lower element on electric tanks, a thermostat set too low, or a tank too small for the household.
What to do: Flushing helps if sediment is the cause. If the tank is over 10–12 years old, it may be time to replace it. See our sizing guide.
Takes a long time to get hot water
What you notice: You wait at the faucet, especially in far bathrooms.
Common causes: Distance from the water heater, a failed recirculation pump or timer, or a tankless unit that needs a moment to fire.
What to do: A recirculation pump brings hot water to far fixtures much faster. If you already have one, the pump or check valve may have failed.
Water too hot, or hot and cold
Water is scalding hot
What you notice: Hot water is hotter than normal, or the relief valve opens.
Common causes: A failed thermostat or gas control, or a mixing valve that stopped mixing.
What to do: Turn the temperature down and call us. Overheating is a safety problem. Read our scald safety tips.
Temperature goes up and down
What you notice: Hot, then cold, then hot again.
Common causes: A failing mixing valve, a thermostat going bad, or on tankless units, scale buildup or a flow rate too low to keep the burner on.
What to do: Text us the type of water heater and when it happens (one fixture or the whole house).
Leaks
Water leaking from the tank itself
What you notice: Water under the tank, rust at the bottom seam, or a wet base.
Common causes: The inner tank has corroded through. This can’t be repaired.
What to do: Close the cold-water valve above the tank, turn the gas to OFF or the breaker off, and call us for a replacement.
Water dripping from the relief valve pipe
What you notice: A small pipe on the side of the tank drips or runs.
Common causes: Water pressure too high, heat expansion with no expansion tank, the water too hot, or a worn relief valve.
What to do: Don’t cap or plug that pipe. It’s a safety valve. We test the pressure and fix the cause. See expansion tanks and relief valves.
Leaks from pipes, fittings or the drain valve
What you notice: Drips at the top connections or the drain valve near the bottom.
Common causes: Loose or corroded fittings, worn water connectors, or a drain valve that won’t seal.
What to do: These are usually repairable without replacing the water heater.
Warm spot on the floor, or the water heater never stops
What you notice: A warm area on the floor, the water heater running or refilling when no one is using hot water, or a gas bill that jumps.
Common causes: A leak in a hot water line under the concrete slab.
What to do: Close the cold-water valve on top of the water heater and call us. See hot water slab leak detection and repair.
Water around a high-efficiency or heat pump unit
What you notice: A puddle near a condensing, tankless or heat pump water heater.
Common causes: Condensate is normal on these units, but a clogged or disconnected condensate drain makes it overflow.
What to do: We clear or reroute the drain. A leak from the unit itself needs a closer look.
Noises
Popping, rumbling or crackling
What you notice: Noise from the tank while it heats.
Common causes: Sediment and hard water scale at the bottom of the tank. Very common with Inland Empire water.
What to do: Flushing can quiet it. Loud rumbling in an older tank often means it’s near the end.
Hissing or sizzling
What you notice: A sizzle from a gas burner or an electric element.
Common causes: Water dripping onto the burner, or scale on an electric element.
What to do: Check for a leak above or around the tank, then text us.
Banging or knocking
What you notice: Bangs in the pipes or the water heater.
Common causes: Water hammer from valves closing quickly, or heavy scale in larger units and boilers.
What to do: Water hammer arrestors or a pressure regulator usually fix pipe banging.
Smelly or discolored water
Hot water smells like rotten eggs
What you notice: The smell is only in the hot water.
Common causes: Bacteria in the tank reacting with the anode rod.
What to do: Replacing the anode rod with a different type and sanitizing the tank usually solves it. If the smell is in the cold water too, the cause is in the water supply.
Rusty or brown hot water
What you notice: Rust-colored water from hot taps only.
Common causes: A worn-out anode rod, a tank starting to rust inside, or old steel pipes.
What to do: See what rusty water means. If the tank is rusting, plan on replacing it.
Sandy bits or white flakes in the water
What you notice: Grit in aerators and showerheads.
Common causes: Sediment from the tank, or a broken dip tube breaking apart.
What to do: Flushing helps with sediment. A broken dip tube gets replaced.
Gas, venting and safety
Soot, scorch marks or a burnt smell near the burner
What you notice: Black marks around the burner door or the top of the tank.
Common causes: Poor venting or backdrafting, a blocked vent or a dirty burner. Exhaust gases can contain carbon monoxide.
What to do: Turn the gas off and call us. Keep a working carbon monoxide alarm in your home.
Power-vent water heater shuts off
What you notice: The blower on top of the tank won’t run, or the unit shows a vent error.
Common causes: A failed blower motor, a bad pressure switch, a blocked vent pipe or condensate in the vent.
What to do: Text us the error code. We test the blower and switch before replacing parts.
Propane water heater problems
What you notice: Weak flame, sooting or no hot water on a propane unit.
Common causes: Low propane supply or pressure, the wrong gas setup, or a dirty burner.
What to do: We test propane pressure and the burner. Never run a natural gas unit on propane without the correct conversion.
Electric problems
Breaker keeps tripping
What you notice: The water heater breaker trips right away or after a while.
Common causes: A shorted heating element, damaged wiring or a loose connection.
What to do: Don’t keep resetting it. Call us so we can test the elements and wiring.
Some hot water, but not much
What you notice: Water is warm, not hot.
Common causes: One of two heating elements has burned out, or one thermostat has failed.
What to do: Elements and thermostats are replaceable. We test both before replacing anything.
Tankless water heaters
Error codes and shutdowns
What you notice: The display shows a code and the water goes cold.
Common causes: Scale buildup, a clogged inlet filter, ignition or flame sensor failure, low gas supply or a venting problem.
What to do: Text us the brand and the code. Many are fixed in one visit. See tankless error codes by brand.
Bursts of cold water
What you notice: Hot, then a shot of cold, then hot again.
Common causes: A small amount of cold water between uses (normal on many units), or scale and low flow keeping the burner from staying on.
What to do: Yearly descaling helps a lot here with our hard water. A small recirculation setup can reduce it.
More on tankless repair and descaling.
Heat pump (hybrid) water heaters
Slow to heat or using more power than expected
What you notice: Hot water takes longer, or the electric bill went up.
Common causes: A dirty air filter, a failed fan or compressor, or the unit running on its backup elements.
What to do: Clean the filter if your model has one, check the operating mode, and text us any error code. More on heat pump water heaters.
Commercial water heaters and hot water boilers
Large commercial units share many of the problems above, plus a few of their own: a lost leg on a three-phase electric heater, low gas pressure when the burner fires, failed blower motors and pressure switches, circulating pumps that quit, and mixing valves that drift. See commercial water heater and boiler repair.
When it’s time to replace instead of repair
Replace the water heater if the tank itself is leaking, or if it’s more than 10–12 years old and needs a major repair. Repair it if it’s younger and the problem is a part such as a thermostat, igniter, gas valve or element. Our guide shows how to read your water heater’s age from the serial number.
We repair every major brand, including A.O. Smith, State, American, Rheem, Ruud, Bradford White, Lochinvar, Rinnai, Takagi, Bosch, GE and Kenmore, and older units such as Mor-Flo, Jetglas and Apollo.
Related
- Water heater guide: age, sizing, flushing and costs
- Tank water heater repair and replacement
- Tankless water heater repair
- Commercial water heaters and boilers
Water heater repair near you:
Questions we hear a lot
How do I know my water heater is going out?
Warning signs include rusty hot water, rumbling noises, water around the base, hot water that runs out faster than it used to, and a tank older than 10–12 years. A leak from the tank itself means it has failed.
Why does my hot water smell like rotten eggs?
Usually bacteria in the tank reacting with the anode rod. Replacing the anode with a different type and sanitizing the tank usually fixes it.
Is it safe to keep using a leaking water heater?
A small leak from a fitting can usually wait a day. A leak from the tank itself can get worse quickly, so close the cold-water valve, shut off the gas or power, and call us.
Can you fix any brand of water heater?
Yes. We are a factory-authorized A.O. Smith contractor, and we repair every major brand of tank, tankless, heat pump and commercial water heater.
Water heater problem? Text us now.
Send a photo of your water heater’s label and tell us what’s happening. A real person texts you back.